The study of the changes in the thermal properties of <Emphasis Type="Italic">Labeo rohita</Emphasis> bones due to arsenic exposure

The paper presents the changes in the thermal properties of control, arsenic exposed and DMSA treated Labeo rohita bones by using thermo analytical techniques. The result shows that the mass loss due to the thermal decomposition occurs in three distinct steps due to loss of water, organic and inorganic materials. The arsenic exposed bones present a different thermal behaviour compared to the control bones. The residue masses are increased due to arsenic exposure, while the DMSA treatment reduces the residue mass level. These thermal characteristics can be used as a qualitative method to check the metal accumulation in samples.     

Anticancer and anti-inflammatory sulfur-containing semisynthetic derivatives of sarcophine

Sarcophine (1), a cembranoid diterpene is known to inhibit the process of tumorigenesis. Sarcophine can be isolated in large amounts from the Red Sea soft coral Sarcophyton glaucum and hence is an ideal target for semisynthetic or biocatalytic modifications. Hydroxylated derivatives of 1 were reported to improve its anticancer activity. Despite the promising results and ready availability, there are limited attempts towards further diversifying the library of sarcophine derivatives. Hence, the current study targets the epoxide ring to generate sulfur-containing derivatives of sarcophine by reacting it with ammonium thiocyanate and Lawesson's reagent. Structure elucidation of the products was based on extensive 1D and 2D NMR and high resolution mass spectrometry, in addition to mechanistic considerations. The effect of these derivatives on highly malignant +SA mammary epithialial cell proliferation is reported. Anti-inflammatory potential of sarcophine and its derivatives is also demonstrated.     

A novel hydrogen-bonded cyclic dibromide in an organic diammonium salt

The organic diammonium salt N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate, (dbtmen)Br₂.2H₂O (1), was prepared by the reaction of N,N,N′,N′-tetramethyl-ethylenediamine (tmen) with benzyl bromide.1 crystallizes in the triclinic space group with the following unit cell dimensions for C₂₀H₃₄Br₂N₂O₂ (M = 494.31):a = 8.6672(6) ?,b = 11.7046(8) ?,c = 11.7731(8) ?, α = 76.988(8)°, β = 88.978(8)°, γ= 76.198(8)γ,V= 1129.26(13) ?³, Z=2. Three components, namely the (dbtmen)²⁺ dication, two bromide anions and two crystal water molecules constitute the structural arrangement of1. H₂O molecules are linked to bromide anions via O-H...Br hydrogen bonding interactions resulting in the formation of a four-membered O₂Br₂ cyclic dibromide. The O₂Br₂ units and the dications are arranged as alternating layers extending in the crystallographicbc plane. The arrangement of anions and cations may be viewed as a typical lamellar structure. The crystal water molecules can be removed by heating 1 at 140°C and the anhydrous dibromide thus formed can be fully rehydrated as evidenced by IR spectra and X-ray powder patterns. Dedicated to Prof S Chandrasekaran on the occasion of his 60th birthday     

FTIR and thermal studies on gel grown neodymium tartrate crystals

The growth of neodymium tartrate crystals was achieved in silica gel by single diffusion method. Optimum conditions were established for the growth of good quality crystals. Fourier transform infrared (FT-IR) spectroscopic study indicates the presence of water molecules and tartrate ligands and suggests that tartrate ions are doubly ionised. The thermal behaviour of the material was studied using thermogravimetry (TG), differential thermal analysis (DTA), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). Thermogravimetric analysis support the suggested chemical formula of the grown crystal to be Nd₂(C₄H₄O₆)₃·7H₂O, and the presence of seven water molecules as water of hydration. It is shown that the material is thermally stable up 45 °C beyond which it decomposes through many stages till the formation of neodymium oxide (Nd₂O₃) at 995 °C. The decomposition pattern is reported to be typical of a hydrated metal tartrate.     

Metal-free N-iodosuccinimide-catalyzed mild oxidative C-H bond amination of benzoxazoles

A facile, efficient, and mild protocol for the synthesis of aminobenzoxazoles has been developed using direct oxidative C-H bond amination of benzoxazoles with secondary or primary amines. The reaction was performed using catalytic amount of N-iodosuccinimide and aqueous hydrogen peroxide as a green oxidant and in the absence of transition metals. Reaction proceeds smoothly at ambient temperature and requires shorter reaction time to furnish excellent yield of the desired products. Various cyclic, acyclic, and functionalized aliphatic amines were well tolerated under optimized reaction conditions and provided good to excellent yield of the respective aminobenzoxazoles.     

Prediction of amount of entrained droplets in vertical annular two-phase flow

Prediction of amount of entrained droplets or entrainment fraction in annular two-phase flow is essential for the estimation of dryout condition and analysis of post dryout heat transfer in light water nuclear reactors and steam boilers. In this study, air–water and organic fluid (Freon-113) annular flow entrainment experiments have been carried out in 9.4 and 10.2 mm diameter test sections, respectively. Both the experiments covered three distinct pressure conditions and wide range of liquid and gas flow conditions. The organic fluid experiments simulated high pressure steam–water annular flow conditions. In each experiment, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using the liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant [Sawant, P.H., Ishii, M., Mori, M., 2008. Droplet entrainment correlation in vertical upward co-current annular two-phase flow. Nucl. Eng. Des. 238 (6), 1342–1352] for the prediction of entrainment fraction is further improved in this study in order to account for the existence of critical gas and liquid flow rates below which no entrainment is possible.Additionally, a new correlation is proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction condition. The improved correlation successfully predicted the newly collected air–water and Freon-113 entrainment fraction data. Furthermore, the correlations satisfactorily compared with the air–water, helium–water and air–genklene experimental data measured by Willetts [Willetts, I.P., 1987. Non-aqueous annular two-phase flow. D.Phil. Thesis, University of Oxford]. However, comparison of the correlations with the steam–water data available in literature showed significant discrepancies. It is proposed that these discrepancies might have been caused due to the inadequacy of the liquid film extraction method used to measure the entrainment fraction or due to the change in mechanism of entrainment under high liquid flow conditions.     

Solvent extraction of uranium(VI) using dibenzo-18-crown-6 in nitrobenzene from ammonium thiocyanate medium

Solvent extraction of uranium(VI) from aqueous solutions of ammoniumthiocyanate has been investigated in the presence of dibenzo-18-crown-6. Uranium(VI)was quantitatively extracted from 1.0M ammonium thiocyanate using 0.01M dibenzo-18-crown-6in nitrobenzene. Back extraction of U(VI) was quantitative with various strippingagents. Separation of U(VI) from other elements was achieved from binary aswell as multicomponent mixtures. Uranium was determined in monazite sand andsyenite rock samples. The method is very simple, rapid and highly reproducible(approximately ±2%).     

Spectrophotometric estimation of rhenium with 5-chloro-2-hydroxythiobenzhydrazide after its extraction separation using n-octylaniline

A solution of n-octylaniline in chloroform extracts rhenium selectively from 0.12–0.16 M nitric acid medium. Rhenium from the organic phase is backstripped with 5% aqueous ammonia solution and estimated spectrophotometrically with 5-chloro-2-hydroxythiobenzhydrazide (5-Cl-2-OHTBH). 5-Cl-2-OHTBH forms a blue complex with rhenium on heating in the acidity range 0.40–3.5 M HCl. The complex is extracted into chloroform and its absorbance is measured at 580 nm. The complex is stable for more than 12 h with a molar extinction coefficient of 9.0 × 10³l mole⁻¹ cm⁻¹ and a Sandell sensitivity of 0.019 μg cm².     

Stabilisation of tetravalent cerium in perchloric acid medium and measurement of the stability constants of its fluoride complexes using ion selective potentiometry

The stability constants of the fluoride complexes of cerium(IV) in 1 M (HClO(4), NaClO(4)) medium have been measured potentiometrically using a fluoride ion-selective electrode. Quantitative oxidation of cerium to its tetravalent state and its stabilisation in the perchlorate medium were accomplished by oxidation with AgO followed by quick addition of a known amount of fluoride ion. This procedure ensures stability of the oxidation state and prevents hydrolysis and polymerisation of Ce(IV). Logarithms of the average values of beta(1), beta(2), beta(3) and beta(4) were estimated to be 7.57+/-0.04, 14.50+/-0.03, 20.13+/-0.37 and 24.14+/-0.10 respectively.     

Studies on fluoride complexing of hexavalent actinides using a fluoride ion selective electrode

Complex formation between actinide(VI) and fluoride ions in aqueous solutions has been investigated using a fluoride ion selective electrode (F-ISE). As fairly high acidity was used to suppress hydrolysis of the actinide(VI) ions, significant liquid junction potentials (E_j) existed in the systems. An iterative procedure was developed for computing free hydrogen ion concentration [H⁺], as it could not be measured directly, using data obtained with F-ISE. E_j values were estimated from known [H⁺] and the stability constants of fluoride complexes of actinide(VI) ions were calculated following KING and GALLAGHER's method using a computer program. The stability constants were found to follow the order U(VI)>Np(VI)>Pu(VI).